ruchi singh - Academia.edu (original) (raw)

Papers by ruchi singh

Acta Metallurgica Et Materialia, 1992

Creep data generated on the materials in the service exposed and the virgin states of a 1 CRY.3 M... more Creep data generated on the materials in the service exposed and the virgin states of a 1 CRY.3 Mo4).25 V steel and also on materials with a wide range of microstructures prepared from the virgin state, have been analysed to determine the resisting stress. The analysis shows that for a given microstructure, as the applied stress increases and reaches a critical value called the transition stress, the creep rate increases sharply from a region of low stress sensitivity to a region of high stress sensitivity. Correspondingly, the resisting stress which increases with applied stress, reaches a threshold value. The results show that, as expected, the transition stress and also the resisting stress in the high stress sensitivity region, depend on the microstructure. However, a remarkable observation is that the resisting stress in the low stress sensitivity region is practically independent of the initial microstructural states investigated. Also the threshold stress is observed to be about 0.5 times the hot yield strength. Based on these observations, a simple method for creep life prediction is proposed.

Scripta Metallurgica Et Materialia, 1990

Morphological and compositional changes of carbides during service can produce deterioration in t... more Morphological and compositional changes of carbides during service can produce deterioration in the creep strength. Their study and characterization are important since they can help residual life assessment[l-3]. The present paper describes the results of T~EDS investigation to study the morphological and compositional changes of carbides in a main steam pipe of ICr-0.3Mo-0.25V ferritic steels after ten years of service.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1991

The morphological and compositional changes of the carbide particles in a ferritic grade of steel... more The morphological and compositional changes of the carbide particles in a ferritic grade of steel have been studied using electron metallography. Specimens were prepared from a main steam pipe in the virgin condition as well as after service exposure in a thermal power plant. The predominantly plate-like vanadium-rich carbide precipitates present in the virgin state showed no significant morphological and compositional changes as a result of the service exposure. On the contrary, a previous investigation of a somewhat different grade of steel reports that as a result of identical service exposure the plate-shaped vanadium-rich carbide transforms into a molybdenum-rich carbide, giving rise to a typical H-type carbide morphology. This difference in the morphological and compositional behaviour of the carbide is attributed to the difference between the compositions of the two steels studied. It appears that the long-term creep strength in some of the Cr-Mo-V ferritic steels, currently in use in the power generation industry, could be improved by a small change in the composition of the steel. 0921-5093/91/$3.50

Journal of Plant Physiology, 2010

Selaginella bryopteris is a lycophyte resurrection plant, which incurves during desiccation and r... more Selaginella bryopteris is a lycophyte resurrection plant, which incurves during desiccation and recovers on availability of moisture. The aim of the study was to test and understand the various physiological and biochemical changes the fronds undergo during desiccation and rehydration, to get an insight as to how this plant adapts and survives through the dry phase. Upon desiccation, S. bryopteris fronds showed drastic inhibition in net photosynthesis (A) and maximal photochemical efficiency of PSII (F(v)/F(m)) however, chlorophyll content did not show much variation. Dark respiration (R(d)) continued even at 10% relative water content (RWC), and showed a burst after rehydration, which is proposed to be crucial to establish protection mechanisms. Desiccation caused an enhanced production of reactive oxygen species (ROS) and increased lipid peroxidation. Proline accumulation increased substantially by 11-fold. Sucrose and starch contents decreased upon desiccation as compared to control. The antioxidative enzymes viz. superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) along with soluble acid invertase increased during desiccation. S. bryopteris shows mechanical as well as physiological mechanisms for tolerance to extreme levels of desiccation stress. The rapid and almost complete recovery of F(v)/F(m) after rehydration clearly indicates the absence of marked photoinhibitory or thermal injury to PSII during desiccation. This along with the homoiochlorophyllous characteristics enables S. bryopteris to recover its A. The antioxidant metabolism further plays an important role in the desiccation tolerance of S. bryopteris.

Experimental Parasitology, 2004

The arbitrary-primed PCR (AP-PCR) technique was employed with the twin goals of identifying genet... more The arbitrary-primed PCR (AP-PCR) technique was employed with the twin goals of identifying genetic polymorphisms within the Indian isolates and to identify differentially expressed gene sequences. The parasite isolates from Indian Kala-azar patients could be differentiated from Leishmania donovani isolates from distinct geographic regions. Moreover, differences within the Indian isolates could also be identified. A majority (17/19) of the Indian isolates gave identical AP-PCR pattern, while two isolates gave consistently divergent pattern. The distinctive AP-PCR fragments obtained with Indian isolates were used as probes in Northern blot analysis. Three such fragments were found to represent transcribed sequences that were differentially expressed in the two stages of the parasite. These sequences led to cloning and characterization of Leishmania Centrin gene and a novel gene termed A-1 that is over-expressed in amastigote stage of the parasite. The study demonstrates the utility of random genome sampling methods in genomic fingerprinting and in identifying differentially transcribed sequences that could potentially contribute to parasite virulence.

Diagnosis -Leishmania -post kala-azar dermal leishmaniasis (PKDL) -visceral leishmaniasis 295 296... more Diagnosis -Leishmania -post kala-azar dermal leishmaniasis (PKDL) -visceral leishmaniasis 295 296 INDIAN J MED RES, MARCH 2006 298 INDIAN J MED RES, MARCH 2006

Transactions of The Royal Society of Tropical Medicine and Hygiene, 2008

Clinical and Vaccine Immunology, 2005

Post-kala-azar dermal leishmaniasis (PKDL) is a dermal complication, a sequel to kala-azar. Diagn... more Post-kala-azar dermal leishmaniasis (PKDL) is a dermal complication, a sequel to kala-azar. Diagnosis of PKDL presents a challenge due to the low parasite burden in the lesions. The direct agglutination test (DAT) based on promastigote and amastigote antigens of Leishmania donovani of indigenous isolates was developed to diagnose PKDL, and the results were compared with those of the rk39 strip test. The sensitivities of DAT for antileishmanial antibody detection, based on promastigote and amastigote antigens at a cutoff titer of 1:800 were 98.5% and 100%, respectively, with corresponding specificities of 96.5% and 100%. DAT could correctly detect 100% polymorphic cases and 95.4% macular PKDL cases. In comparison, the rk39 strip test was able to correctly diagnose 95.6% of polymorphic and 86.0% macular PKDL cases. DAT based on axenic amastigote antigen provided 100% sensitivity and specificity, making it particularly useful for macular PKDL cases, which are often missed by the rk39 strip test. Thus, DAT provides a simple, reliable, and inexpensive test for PKDL diagnosis with potential applicability in field conditions.

$Research paper thumbnail of Visceral Leishmaniasis, or Kala Azar (KA): High Incidence of Refractoriness to Antimony Is Contributed by Anthroponotic Transmission via Post‐KA Dermal Leishmaniasis$

Journal of Infectious Diseases, 2006

individuals with post-KA dermal leishmaniasis (PKDL) are considered to be reservoirs of transmiss... more individuals with post-KA dermal leishmaniasis (PKDL) are considered to be reservoirs of transmission of Leishmania donovani in India. When intracellular amastigotes were used to assess the natural susceptibility that PKDL isolates and KA isolates have to sodium antimony gluconate (SAG), the mean ED 50 was found to be and mg/ 12.0 ‫ע‬ 2.49 11.0 ‫ע‬ 1.38 mL, respectively; and there was a significant correlation with the clinical response ( ). All KA isolates, as well r p 0.99 rank as a significant proportion (55%) of PKDL isolates from high-endemicity zones, were resistant to SAG. The median ED 50 for SAG-resistant PKDL isolates (20.0 mg/mL) was significantly higher ( ) than that for SAG-resistant KA P ! .05 isolates (15.7 mg/mL). SAG-resistant PKDL isolates may contribute to KA's increased refractoriness to SAG, via anthroponotic transmission of SAG-resistant strains.

We report here the identification of polymorphism in a well-defined genetic locus among the Leish... more We report here the identification of polymorphism in a well-defined genetic locus among the Leishmania parasites causing the visceral and dermal manifestations, in a comparison of 15 post-kala-azar dermal leishmaniasis and 12 kala-azar patient isolates.

Antimicrobial Agents and Chemotherapy, 2009

These include: REFERENCES http://aac.asm.org/content/53/2/835#ref-list-1 at:

Microbes and Infection, 2006

Five to fifteen percent of visceral leishmaniasis (VL) patients in India develop post kala-azar d... more Five to fifteen percent of visceral leishmaniasis (VL) patients in India develop post kala-azar dermal leishmaniasis (PKDL), usually 1e2 years after apparent clinical cure. There is evidence pointing to a role played by the host immune responses in the disease pathogenesis, however, the contribution of changes in parasite gene expression has not been explored. Highly sensitive gene expression microarray technology was employed to identify genes that are differentially expressed in Leishmania parasites isolated from PKDL patients in comparison with those from VL. Hybridization on Leishmania donovani genomic microarray comprised of unique clones allowed us to identify 46/2268 (2%) clones that showed statistically significant (P < 0.05) changes in expression (1.5e3.5-fold) in parasites of PKDL origin compared to those of VL origin. Sequence analysis of six genomic clones, consistently showing approximately 2-fold higher expression in PKDL parasites, revealed significant homology with gp63, gp46, putative amastin, a putative reductase and a possible calpain-like protein. The gene products showing upregulated expression in PKDL isolates may be candidates playing a role in the altered clinical manifestation in PKDL. Such differentially expressed genes hold the key to understanding the parasite genetic factors that contribute to the persistence after clinical cure of VL.